Siemens SINAMICS G120 Operating Instructions Manual page 373

Note
When compared to closed-loop control with encoder, the dynamic response for sensorless
motors is significantly reduced. This is because the speed can only be derived from the
inverter output quantities for current and voltage which have the appropriate noise level.
Speed controller pre-control (P1496, P0341, P0342)
The control behavior of the speed control loop can be improved if the speed controller of the
inverter also generates values for the current setpoints (corresponds to the torque setpoint)
from the speed setpoint. The torque setpoint m
This is entered into the current controller through an adaptation element directly as an
additive control quantity (this is enabled using P1496).
The motor moment of inertia P0341 is directly calculated during the quick commissioning or
the complete parameterization (P0340 = 1). The factor P0342 between the total moment of
inertia and motor moment of inertia must be manually determined.
Figure 8-93
When correctly adapted, the speed controller only has to correct noise
quantities/disturbances in its control loop and this is achieved with a relatively low
manipulated quantity change. On the other hand, speed setpoint changes bypass the speed
controller and are therefore executed faster.
The effect of the pre-control quantity can be adapted, depending on the particular
application, using the pre-control factor P1496. Using P1496 = 100 %, the pre-control is
calculated according to the motor and load moment of inertia (P0341, P0342). In order that
the speed controller does not work against the torque setpoint which is entered, a balancing
filter is automatically used. The time constant of the balancing filter corresponds to the
Control Units CU240S
Operating Instructions, 11/2006, A5E00766042B AA
Speed controller with pre-control
8.24 Open-loop and closed-loop control
, is calculated as follows:
v
Functions
8-177